The scientific objective of the Add Health Wave V Program Project is to understand the early life precursors of chronic disease by tracing the cumulative and integrated biological, behavioral, and psychosocial processes that are hypothesized to operate in all stages of the life course. Evidence indicates that early life circumstances are related to disease susceptibility later in life, yet the mechanisms through which early life conditions influence the emergence of chronic disease are relatively unknown. At the same time, increasing evidence indicates that chronic conditions are occurring at younger ages in the US, with rates of hypertension, diabetes, stroke, and kidney disease rising among young adults. Most research links childhood exposures to adult chronic disease without any attention to the formative life stages of adolescence and the transition to adulthood and their role in predisease pathways. The nationally representative, longitudinal, multilevel design of Add Health is well suited to address this scientific gap. We propose to collect a fifth follow-up wave of interviews with original Wave I Add Health respondents over the period from 2015 to 2018 when they will be 31-42 years old. We employ new data collection innovations at Wave V that are practical and maintain data quality integrity and will benefit the field of survey research and methodology. The Wave V Program Project has three goals: 1) Re-interview Add Health cohort members in a Wave V follow-up to collect social, environmental, behavioral, and biological data with which to track the emergence of chronic disease and disease risk as the cohort moves through its fourth decade of life (Projects I, IV); 2) Build upon the life course history of Add Health respondents by adding and refining early-life measures of their birth and childhood circumstances to create a 40-year longitudinal record on the Add Health cohort from birth through the fourth decade of life (Projects I, II, Ill); 3) Integrate the data collected in Projects I, II, and IV with existing longitudinal data on Add Health respondents and their parents to conduct transformative research on the early life precursors of chronic disease using dynamic, multilevel, inter-generational longitudinal analysis (Project Ill).